IAC\Idle your thoughts?

[jtlinna]

I've tried to adjust my idle per service guide. Adjust the screw and the idle will change. I shut the car off. Remove the jumper wire and reset the ECU. After the relearn the idles back to around the 700 mark.

So i found this at work. (See Attached) Not sure what to make of it. If the IAC controls the idle isnt it always going to try and keep a preset idle number?

Also sorry for the scanned photo. I can type out what it says if needed..

JT

 

[kamesama980]

The problem they're having was when the throttle's closed it idles high, then drops down after a moment. Reason being the throttle opening % when released was too much. IE at idle more air is going through the throttle than the IAC...seems like half a dozen one way, six the other way but when you're on the gas the IAC is usually wide open. so when you let off, you have max IAC plus the throttle, which in this case was more than designed, causing too-high idle 'till the IAC responded and closed down.

 

[RABID_MP5]

So is the idle air screw controlling a separate path for idle air then the IAC itself? Where is it located? Would this setting also explain revs that kick up a bit between shifts?

 

[traaben]

my 2004 mazda 3 will accelerate up and down while im driving and when i try to stop its rpms run high making it hard to stop.. it so bad i sometimes have to turn the ignition off to ensure that i can stop the car! does anyone know what this could be???

 

[jtlinna]

The problem they're having was when the throttle's closed it idles high, then drops down after a moment. Reason being the throttle opening % when released was too much. IE at idle more air is going through the throttle than the IAC...seems like half a dozen one way, six the other way but when you're on the gas the IAC is usually wide open. so when you let off, you have max IAC plus the throttle, which in this case was more than designed, causing too-high idle 'till the IAC responded and closed down.

Kinda lost me. What im seeing is that when they let off the throttle theres too much air bypassing the throttle plate and gives a high idle.. the IAC then lowers its % open at idle to drop the idle rpms to get i back to its 700rpm +/- 50rpms. The point im was trying to get at is i cant adjust my idle. The scan tool shows the IAC will adjust its %open to bing the idle back to its factory setting no matter how high i set it per the manual..

In no way am i trying to be a jerk and i thank you for your responce.. Im trying to figure this thing out. lol

JT

 

[jtlinna]

for anyone that reads this never touch the allen screw and lock nut for the throttle plate. Its not how you adjust your idle and its a huge no no and will screw up youe TPS and probly other things.

 

[jtlinna]

my 2004 mazda 3 will accelerate up and down while im driving and when i try to stop its rpms run high making it hard to stop.. it so bad i sometimes have to turn the ignition off to ensure that i can stop the car! does anyone know what this could be???

i know little about the mazda3. but its a mazda so check for vaccume leaks first. also any codes.

 

[Fresco]

my 2004 mazda 3 will accelerate up and down while im driving and when i try to stop its rpms run high making it hard to stop.. it so bad i sometimes have to turn the ignition off to ensure that i can stop the car! does anyone know what this could be???

You should never turn your car off while trying to slow down, what if you have to avoid hitting something how do you expect to steer out of the way?......worse case scenerio put the car in neutral and you can slow down like that and if the problem is as bad as you say take to someone and have the look what the problem may be

 

[RABID_MP5]

+1 The steering wheel can lock and then you can have a very bad day.

 

[whatusername]

for anyone that reads this never touch the allen screw and lock nut for the throttle plate. Its not how you adjust your idle and its a huge no no and will screw up youe TPS and probly other things.

are u kidding me? i just adjusted the hell out of that thuing and found it idle up nice then shut cat off n have the same low idle issue as before so i adjust more n more and it all repeats

 

[iluvmacs]

The screw adjusts the back stop for the throttle plate. If you turn it clockwise, it opens the throttle, effectively increasing the air that passes when you are at zero throttle. If you turn it counter-clockwise, it will allow the springs to close the throttle, but there's then a chance that the force will allow the plate to stick to the throttle. The IAC valve should be able to handle engine idle with the throttle 99.9% closed. That last 0.1% is to keep the plate from contacting the bore of the throttle where it can mechanically stick shut.

The manual says not to adjust, but you can fix it if you did adjust it. It's easiest to do with the throttle body off the car. turn it clockwise until you see the throttle open. then turn it counter clockwise until when allowing the spring to snap the plate to the closed position, the sound changes from the stop screw to the plate hitting the throttle bore. Then put the screw half way between these two positions. You can't adjust while the car is running, because the IAC will do the exact opposite that you do to maintain idle.